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synchronized

news 2026/3/27 0:31:39

几种方式

修饰方法

同一个实例，同一时间只能有一个线程访问该方法作用域是同一个实例

package com.jysemel.java.basic.thread.lock;import lombok.SneakyThrows;import java.util.concurrent.TimeUnit;public class SynchronizedDemo1 {@SneakyThrowspublic synchronized void say() {System.out.println("static1 -------------" + Thread.currentThread().getName());TimeUnit.SECONDS.sleep(10);System.out.println("static1-----------------end" + Thread.currentThread().getName());}public static void main(String[] args) {// 同一个实例SynchronizedDemo1 demo1 = new SynchronizedDemo1();new Thread(demo1::say).start();new Thread(demo1::say).start();// 不同实例SynchronizedDemo1 demo2 = new SynchronizedDemo1();SynchronizedDemo1 demo3 = new SynchronizedDemo1();new Thread(demo2::say).start();new Thread(demo3::say).start();}
}

修饰静态方法

作用域全局

package com.jysemel.java.basic.thread.lock;import lombok.SneakyThrows;import java.util.concurrent.TimeUnit;public class SynchronizedDemo2 {@SneakyThrowspublic static synchronized void say() {System.out.println("static1 -------------" + Thread.currentThread().getName());TimeUnit.SECONDS.sleep(10);System.out.println("static1-----------------end" + Thread.currentThread().getName());}public static void main(String[] args) {new Thread(SynchronizedDemo2::say).start();new Thread(SynchronizedDemo2::say).start();}
}

修饰代码块(同步代码块)

同一个实例，同一时间只能有一个线程访问该方法如果是静态对象，则作用域全局

package com.jysemel.java.basic.thread.lock;import lombok.SneakyThrows;import java.util.concurrent.TimeUnit;public class SynchronizedDemo3 {private final Object obj = new Object();private final static Object staticObj = new Object();@SneakyThrowspublic void say(String name) {synchronized (obj) {System.out.println(name + "say -------------" + Thread.currentThread().getName());TimeUnit.SECONDS.sleep(10);System.out.println(name + "say-----------------end " + Thread.currentThread().getName());}}@SneakyThrowspublic void staticSay(String name) {synchronized (staticObj) {System.out.println(name + "staticSay -------------" + Thread.currentThread().getName());TimeUnit.SECONDS.sleep(10);System.out.println(name + "staticSay-----------------end " + Thread.currentThread().getName());}}public static void main(String[] args) {
//        // 同一个实例
//        SynchronizedDemo3 demo1 = new SynchronizedDemo3();
//        new Thread( () -> demo1.say("thread1 ")).start();
//        new Thread( () -> demo1.say("thread2 ")).start();
//
//        //不同实例
//        SynchronizedDemo3 demo2 = new SynchronizedDemo3();
//        SynchronizedDemo3 demo3 = new SynchronizedDemo3();
//        new Thread( () -> demo2.say("thread3 ")).start();
//        new Thread( () -> demo3.say("thread4 ")).start();//不同实例，静态对象SynchronizedDemo3 demo4 = new SynchronizedDemo3();SynchronizedDemo3 demo5 = new SynchronizedDemo3();new Thread( () -> demo4.staticSay("thread4 ")).start();new Thread( () -> demo5.staticSay("thread5 ")).start();System.out.println("finished");}}

修饰代码块(this和类)

同一个实例，同一时间只能有一个线程访问该方法类，则作用域全局

package com.jysemel.java.basic.thread.lock;import lombok.SneakyThrows;import java.util.concurrent.TimeUnit;public class SynchronizedDemo4 {@SneakyThrowspublic void say(String name) {synchronized (this) {System.out.println(name + "say -------------" + Thread.currentThread().getName());TimeUnit.SECONDS.sleep(10);System.out.println(name + "say-----------------end " + Thread.currentThread().getName());}}@SneakyThrowspublic void staticSay(String name) {synchronized (SynchronizedDemo4.class) {System.out.println(name + "staticSay -------------" + Thread.currentThread().getName());TimeUnit.SECONDS.sleep(10);System.out.println(name + "staticSay-----------------end " + Thread.currentThread().getName());}}public static void main(String[] args) {// 同一个实例SynchronizedDemo3 demo1 = new SynchronizedDemo3();new Thread( () -> demo1.say("thread1 ")).start();new Thread( () -> demo1.say("thread2 ")).start();//不同实例SynchronizedDemo3 demo2 = new SynchronizedDemo3();SynchronizedDemo3 demo3 = new SynchronizedDemo3();new Thread( () -> demo2.say("thread3 ")).start();new Thread( () -> demo3.say("thread4 ")).start();//不同实例，静态对象
//        SynchronizedDemo4 demo4 = new SynchronizedDemo4();
//        SynchronizedDemo4 demo5 = new SynchronizedDemo4();
//        new Thread( () -> demo4.staticSay("thread4 ")).start();
//        new Thread( () -> demo5.staticSay("thread5 ")).start();System.out.println("finished");}}